diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/send.c | 127 |
1 files changed, 92 insertions, 35 deletions
@@ -23,6 +23,8 @@ #include <unistd.h> #include <stdlib.h> #include <string.h> +#include <alloca.h> +#include <getopt.h> #include <math.h> /* -lm */ #include <alsa/asoundlib.h> /* dep: alsa-lib (pkg-config alsa) */ @@ -37,9 +39,6 @@ #define DURATION 100 /* ms */ /* 100 ms → 10 Bd → 5 B/s */ #define LATENCY 100000 /* µs */ -#define PARITY 2 -#define USE_EXTRA_PARITY 0 - /** @@ -64,6 +63,42 @@ static snd_pcm_t* sound_handle = NULL; */ static UTYPE buffers[16][N]; +/** + * The number of parity tones in the hamming code. + */ +static int parity = 3; + +/** + * Whether to add an additional parity tone (of all + * data tones) in addition to those numerated by `parity`. + */ +static int use_extra_parity = 0; + +/** + * Whether to add redundancy frequencies in the tones. + */ +static int use_redundant_freq = 0; + +/** + * Data buffer used for error correcting code support. + */ +static int* data; + +/** + * Code buffer used for error correcting code support. + */ +static int* code; + +/** + * The number elements that can be stored in `data`. + */ +static int data_n; + +/** + * The number elements that can be stored in `code`. + */ +static int code_n; + /** @@ -111,10 +146,15 @@ static void init_buffers(void) buffer = buffers[j]; get_freq(j, &low, &high); - for (i = 0; i < N; i++) - buffer[i] = (GENERATE_TONE(low * 1) + GENERATE_TONE(high * 1) + - GENERATE_TONE(low * 4) + GENERATE_TONE(high * 4)) * - (SMAX / 4) - SMIN; + if (use_redundant_freq) + for (i = 0; i < N; i++) + buffer[i] = (GENERATE_TONE(low * 1) + GENERATE_TONE(high * 1) + + GENERATE_TONE(low * 4) + GENERATE_TONE(high * 4)) * + (SMAX / 4) - SMIN; + else + for (i = 0; i < N; i++) + buffer[i] = (GENERATE_TONE(low * 1) + GENERATE_TONE(high * 1)) * + (SMAX / 2) - SMIN; } } @@ -154,6 +194,9 @@ static int send_nibble(int n) */ static int send_byte(int c) { +#ifdef DEBUG + fprintf(stderr, "%s: sending byte: %i\n", argv0, c); +#endif if (send_nibble((c >> 0) & 0x0F)) return -1; if (send_nibble((c >> 4) & 0x0F)) return -1; return 0; @@ -177,43 +220,42 @@ static int send_byte(int c) */ static int send_byte_with_ecc(int c) { -#if PARITY < 2 - if (send_byte(c)) - return -1; -# if PARITY == 1 - if (send_byte(c)) - return -1; -# endif -# if USE_EXTRA_PARITY == 1 - if (send_byte(c)) - return -1; -# endif - return 0; - -#else - static int data[(1 << PARITY) - PARITY - 1]; static int ptr = 0; - static int code[(1 << PARITY) - 1 + USE_EXTRA_PARITY]; int i, j, d, p; + if (parity < 2) + { + if (c < 0) + return 0; + if (send_byte(c)) + return -1; + if (parity) + if (send_byte(c)) + return -1; + if (use_extra_parity) + if (send_byte(c)) + return -1; + return 0; + } + /* Fill buffer. */ if (c < 0) { if (ptr > 0) - while (ptr < sizeof(data) / sizeof(*data)) + while (ptr < data_n) data[ptr++] = -c; } else data[ptr++] = c; /* Is it full? */ - if (ptr < sizeof(data) / sizeof(*data)) + if (ptr < data_n) return 0; ptr = 0; /* Hamming code. */ - memset(code, 0, sizeof(code)); - for (i = 1, j = 0; i <= (1 << PARITY) - 1; i++) + memset(code, 0, code_n * sizeof(*code)); + for (i = 1, j = 0; i <= (1 << parity) - 1; i++) { if ((i & -i) == i) continue; @@ -223,18 +265,16 @@ static int send_byte_with_ecc(int c) code[i - 1] = data[j]; j++; } -# if USE_EXTRA_PARITY == 1 - for (i = 0; i < sizeof(data) / sizeof(*data); i++) - code[(1 << PARITY) - 1] ^= data[i]; -# endif + if (use_extra_parity) + for (i = 0; i < data_n; i++) + code[(1 << parity) - 1] ^= data[i]; /* Transmit. */ - for (i = 0; i < sizeof(code) / sizeof(*code); i++) + for (i = 0; i < code_n; i++) if (send_byte(code[i])) return -1; return 0; -#endif } @@ -337,8 +377,8 @@ static int send_term(void) /** * Transmit a file over audio. * - * @param argc Not used for anything else than the process name. - * @param argv Not used for anything else than the process name. + * @param argc The number of elements in `argv`. + * @param argv Command line arguments. * @return 0 on success, 1 on failure. */ int main(int argc, char* argv[]) @@ -346,7 +386,19 @@ int main(int argc, char* argv[]) struct sigaction act; int r, rc = 1; + /* Parse command line. */ argv0 = argc ? argv[0] : ""; + for (;;) + { + r = getopt (argc, argv, "fpr:"); + if (r == -1) + break; + else if (r == 'f') use_redundant_freq = 1; + else if (r == 'p') use_extra_parity = 1; + else if (r == 'r') parity = atoi(optarg); + else if (r != '?') + abort(); + } /* Set up signal handling. */ siginterrupt(SIGTERM, 1); @@ -363,6 +415,11 @@ int main(int argc, char* argv[]) /* Generate the tones to play. */ init_buffers(); + /* Generate buffers for error correcting code. */ + data_n = (1 << parity) - parity - 1; + code_n = (1 << parity) - 1 + use_extra_parity; + data = alloca(data_n * sizeof(*data)); + code = alloca(code_n * sizeof(*code)); /* Set up audio. */ r = snd_pcm_open(&sound_handle, "default", SND_PCM_STREAM_PLAYBACK, 0); |